In todays world you cannot easily have 'manual reversion ' and certainly not to pen and paper.
I have been in telecoms for 35 odd years and back in the 60s AT&T/Bell telephone realised that if direct dialling 'broke' every woman (no sexism then) in the USA would have to be a telephone operator (I realsie if you are under 40 odd you ahve no idea about that)
In these cases of massive complexity you have a number of strategic issues you must deal with
1 You cannot skimp on diversity and redundancy cost money
2 You cannot keep bodging systems to work together -you will never be rid of all add on s but you can ensure a stable core through redundancy of computers and interconnecting telcoms networks. Cost a lot of money.
3 you have to maintain a substantial core of staff who ar expert and experienced on your systems because they are all different in some way. Outsourcing and working to SLA for any complex activity is the road to disaster
4 Someone at board level has to understand all this and have a lot of influence to stop the spread of 'can't you do it cheaper' prevalent in UK companies compared to can't you do it better.
5 You must proactively hunt down problems as referred to earlier with Netflix , you need skilled staff to do this safely and securely and they are not cheap
6. If you look at Google . Facebook Amazon etc they have massive global networks with 'mirrors all over the world so there is no single point of failure. Everything on one mega server/data centre is backed up on another on in a different country or continent. This costs a lot of money but because of their cash position and stock values they can afford it
7 Recognise that IT for an airline is at the heart of everything. marketing is based on your customer data, sales are transacted through it. the passenger side of the system feeds the ops side with pax count , baggage weight and numbers that all affects fuel and weight and balance etc etc etc
So it is not just important it is at the heart of the operation but I bet the CFO and head of sales and Marketing earn more than the head of IT and that CEO has not got a clue about the issue.
Incidentally where is he -talk about leading from the bunkers